Compact polyphase optical position encoder

Abstract

A compact polyphase optical encoder subassembly for installation in host equipment is disclosed. The subassembly includes a moveable scale; and, a unitized rotatable housing for aligning a light source, a mask and a photodetector array having at least a pair of photodetector areas symmetrically disposed about an axis of rotation of the housing and responsive to light energy from the light source in further response to relative position of the scale. The housing further includes in its preferred form a bolt having a widened head and a threaded shank for passing through an opening in a base of the host, a threaded nut engageable with the shank opposite to the head for thereby securing the bolt to the base, and a compressible washer for enabling a predetermined range of vertical compression between the head and the base as the nut is tightened on said shaft. The housing further includes a light source holder which in preferred form comprises a central support, a reflective surface in optical alignment with the photodetector array and being aligned and supported by the central support, and a lateral arm spaced away from the central support, the lateral arm for holding the light source in optical alignment with the reflective surface, whereby the subassembly may be made very compact in terms of height and still provide a substantial distance between the light source and the mask, thereby minimizing penumbra effects.

We claim: 
     
       1. A compact polyphase optical position encoder subassembly for installation in and use with host equipment including a base and a moveable, edge mounted scale with alternating equally dimensioned opaque and translucent regions extending generally perpendicular to a locus of scale movement in a dimension generally parallel to a mounting portion of the base; said subassembly comprising: a unitized rotatable housing for aligning a light source, a mask and a photodetector array having at least a pair of photodetector areas symmetrically disposed oppositely about an axis of rotation of said housing and responsive to light energy from said light source as modified by relative position of said scale, said housing including:   a bolt having a widened head and a threaded shank for passing freely through an opening defined in the mounting portion of the base of said host equipment,   a threaded nut engageable with said threaded shank opposite to said widened head when said bolt is seated through said opening for for adjusting the height of said bolt relative to said base, and   compressible bias force providing means compressible between said base and said bolt for enabling a predetermined range of vertical adjustment between said widened head and said base as said nut is rotated about said threaded shank to compress said bias force providing means;   said housing further including a cell holder mounted to said widened head for holding said photodetector array and said mask in predetermined proper optical alignment about said axis of rotation,   said housing further including a light source holder mounted to said cell holder for holding said light source a predetermined distance away from said cell holder in proper optical alignment, said cell holder and said light source holder defining a transverse opening enabling said scale to pass freely along its locus of movement adjacent to said mask,   whereby rotation of said housing facilitates phase lead-lag trim between the poly phases put out by said photodetector array and compression of said bias force providing means controls gap spacing between said scale and said mask.   
     
     
       2. The compact subassembly as set forth in claim 1 wherein said light source holder comprises a central support, a reflective surface in optical alignment with said photodetector array and being aligned and supported by said central support, and a lateral arm spaced away from said central support, said lateral arm for holding a said light source in optical alignment with said reflective surface, whereby said subassembly may be made very compact in terms of height and still provide a substantial distance between the light source and the mask, thereby minimizing penumbra effects. 
     
     
       3. The compact subassembly as set forth in claim 1 wherein said compressible bias force providing means comprises a wave spring washer. 
     
     
       4. A compact polyphase optical encoder subassembly for installation and use with host equipment including a base and a moveable, edge mounted scale with alternating equally dimensioned opaque and translucent regions extending generally perpendicular to a locus of scale movement in a dimension generally parallel to a mounting portion of the base; said subassembly comprising: a unitized rotatable and height adjustable housing for aligning and supporting a light source, a mask and a photodetector array having at least a pair of photodetector areas symmetrically disposed about an axis of rotation of said housing and responsive to light energy from said light source in further response to relative position of said scale, said housing being rotatably alignable and height adjustable with respect to said mounting portion and including: a cell holder mounted to said housing for holding said photodetector array and said mask in a predetermined proper alignment,   said housing further including a light source holder mounted to said cell holder for holding said light source a predetermined distance away from said cell holder, said cell holder and said light source holder defining a transverse opening enabling said scale to pass freely along its locus of movement adjacent to said mask,   said light source holder comprising a central support, a reflective surface in optical alignment with said photodetector array and being aligned and supported by said central support, and a lateral arm spaced away from said central support, said lateral arm for holding said light source in optical alignment with said reflective surface and said photodetector array,   whereby said subassembly may be made very compact in terms of height and still provide a substantial distance between the light source and the mask, thereby minimizing penumbra effects.     
     
     
       5. The compact polyphase optical encoder subassembly as set forth in claim 4 wherein said housing includes a bolt having a widened head and a threaded shank for passing freely through an opening defined by said mounting surface in said base of said host equipment, a threaded nut engageable with said threaded shank opposite to said widened head for adjusting the height of said bolt relative to said base, and compressible washer means for enabling a predetermined range of vertical compression between said widened head and said base as said nut is tightened on said shaft, whereby rotation of said housing facilitates phase lead-lag trim of said subassembly and compression of said washer means controls spacing between said scale and said mask.